还原可降解聚磺酸甜菜碱型纳米水凝胶的制备及载药研究

目的:制备与表征还原可降解的聚磺酸甜菜碱型纳米水凝胶,利用该纳米递药系统包载阿霉素(DOX)并初步评价其抗肿瘤性能。方法:利用回流沉淀聚合的方法合成含二硫键的聚磺酸甜菜碱甲基丙烯酸酯(PSBMA)纳米水凝胶及不含二硫键的PSBMA纳米凝胶(nd-PSBMA);通过粒度仪和透射电镜考察两种纳米水凝胶的粒径、形态以及稳定性;通过考察谷胱甘肽(GSH)对纳米凝胶溶液相对浊度的影响以评价还原环境对两种纳米凝胶的还原可降解性;利用纳米凝胶包载阿霉素(DOX),考察载药凝胶在GSH中的释药行为,并初步评价其对A549肿瘤细胞的杀伤作用。结果:以N, N'-双丙烯酰胱胺为交联剂制备了含二硫键的PSBMA纳米凝胶,其粒径在180～200 nm;同时以N, N'-双丙烯酰胺为交联剂制备了不含二硫键的n-PSBMA纳米凝胶。两种纳米凝胶与小鼠血清共孵育7天水合粒径仍无明显变化,表明磺酸甜菜碱型纳米凝胶具有良好的抗蛋白吸附能力。此外,PSBMA纳米凝胶在GSH溶液中迅速地降解,且降解速度与GSH浓度呈正相关;而nd-PSBMA纳米凝胶在GSH溶液中几乎不降解。载DOX的PSBMA纳米凝胶可在GSH作用下快速的释放药物而载DOX的nd-PSBMA纳米凝胶在GSH作用下缓慢的释放药物;体外细胞实验显示空白纳米凝胶和载药nd-PSBMA对A549细胞无明显毒性作用,但载DOX的PSBMA纳米凝胶可高效地杀死A549肿瘤细胞,其药效与游离DOX相仿。结论:还原可降解的PSBMA纳米水凝胶有望成为智能型控释药物载体。     

可注射更昔洛韦温敏型原位凝胶剂的研究

目的：构建温敏型三嵌段共聚物,研究其理化性质以及用其制备的可注射更昔洛韦温敏型原位凝胶剂的制剂特性。方法：以聚乙二醇（PEG）作为亲水嵌段,丙交酯（LA）和β- 丁内酯（β-BL）的无规共聚物PBLA 作为疏水嵌段,采用开环聚合法合成温敏型三嵌段共聚物PBLA-PEG-PBLA,并对其理化性质进行表征,考察其溶液的胶凝温度/ 临界凝胶浓度、流变学性质、通针性和溶蚀行为以及以更昔洛韦作为模型药物、用其制得的可注射载药温敏型原位凝胶剂的体外释放特性。结果：合成的PBLA-PEG-PBLA 嵌段共聚物重均分子质量在6 000 左右,多分散系数为1.5 左右;其溶液临界凝胶浓度（g?mL-1）为5%~10%,质量浓度（g?mL-1）在10%~25% 时胶凝温度为31~35 ℃,接近并略低于体温;其凝胶在低温下储能模量与黏度较小,当温度接近相转变温度后两者迅速增大;其载药凝胶剂累计释放量经拟合显示遵循一级动力学方程,并呈扩散释药机制。结论：较低质量浓度[10%~15%（g?mL-1）] 的PBLA-PEG-PBLA 更符合玻璃体注射要求,更适用于制备可注射载药温敏型原位凝胶剂。     

D-甘露糖修饰聚合物胶束的制备及其在靶向药物输送中的应用

聚合物胶束作为药物载体具有良好的稳定性和生物相容性,提高疏水性药物溶解性等优势,是一类很有应用潜力的药物传输系统。本研究以合成的共价键连D-甘露糖的双亲性聚合物分子(PGMA-Mannose)为药物载体,包载抗癌药物阿霉素(DOX)制备具有甘露糖受体靶向性和pH敏感药物释放特性的新型载药聚合物胶束。利用激光共聚焦显微镜和MTT细胞毒性评价方法对载药胶束的细胞内吞摄取和毒性进行评价。实验结果表明,载药胶束能特异性识别人乳腺癌细胞MDA-MB-231表面过度表达的甘露糖受体,被癌细胞大量摄取并在细胞溶酶体酸性环境内释放药物,而载药胶束在表面甘露糖受体低表达的HEK293细胞中只有少量摄取。与原药DOX相比,该载药胶束对癌细胞的毒性显著提高,而对正常细胞的毒性较低。因此,该PGMA-Mannose聚合物胶束有望成为一种新型的靶向药物输送系统应用于癌症的治疗。     

原位可注射壳聚糖基温敏水凝胶的制备及其在预防ESD术后食管狭窄中分阶段释药应用研究

摘要 目的：构建一种可以分阶段释放药物的原位可注射水凝胶，通过直接注射在ESD（Endoscopic Submucosal Dissection，内镜黏膜下剥离术）术后伤口处，形成水凝胶敷料，起到保护伤口的作用。同时凝胶中的两种药物通过分阶段释放的方式，更好地促进伤口的无瘢痕愈合，为ESD术后食管狭窄的预防提供一种新的参考方案。方法：在壳聚糖/β-甘油磷酸钠（CS/β-GP）温敏水凝胶的体系中加入聚多巴胺（PDA），制备壳聚糖/β-甘油磷酸钠/聚多巴胺（CS/?β-GP/PDA）水凝胶。通过在载药水凝胶中加入聚乙二醇-聚乳酸-羟基乙酸（PEG-PLGA）纳米载药微粒制备CS/β-GP/PDA/NPs双载药水凝胶，通过两种载药体系的复合，实现药物的分阶段释放。通过流变学实验测定CS/β-GP、CS/β-GP/PDA、CS/β-GP/PDA/NPs凝胶体系的相转变温度以及凝胶强度。通过高效液相色谱法检测CS/β-GP/PDA/NPs水凝胶中两种药物的释放动力学特征。通过CCK-8细胞增殖实验评价CS/β-GP/PDA、CS/β-GP/PDA/NPs温敏水凝胶的生物相容性。在体外猪食管中，模拟ESD术后创口，通过内镜辅助将水凝胶母液注射在伤口处，并通过内镜观察水凝胶的凝胶状态。结果：得到了粘附性显著增强的壳聚糖/β-甘油磷酸钠/聚多巴胺（CS/β-GP/PDA）凝胶体系。流变学实验证明聚多巴胺（PDA）的加入可以显著降低水凝胶的凝胶温度，缩短原位成胶时间。CCK-8实验显示CS/β-GP/PDA、CS/β-GP/PDA/NPs凝胶体系无潜在的细胞毒性。在体外猪食管模拟实验中，将其凝胶母液注射在伤口处后，可原位形成凝胶，且凝胶贴合伤口，具有较强的粘附性。通过体外释药速率测定，验证了CS/β-GP/PDA/NPs水凝胶中所载两种药物释放速率存在明显差异，可实现药物的分阶段释放。结论：设计的CS/β-GP/PDA/NPs凝胶体系适用于ESD术后的伤口修复，并能够实现分阶段释药，对于预防ESD术后食管狭窄具有潜在的应用价值。     

生物医用高分子材料在药物控释系统中的应用

药物控制释放体系是继传统载药体系发展起来的一种新型的疾病治疗体系。生物医用高分子材料作为药物控释载体的研究逐渐成为热点之一。近年来,随着研究的深入,生物医用高分子材料在药物控释系统中的运用得到了广泛的发展。本文简要介绍了常用天然医用高分子材料如胶原、纤维素以及环糊精和合成医用高分子材料如聚乳酸、聚酸酐等在药物控释系统中的应用,并对这类材料的应用进行了展望。     

聚合物脂质纳米球的制备优化

目的:制备粒径均一且稳定、载药率和包埋率较高的聚合物脂质纳米球。方法:将HSPC(氢化大豆卵磷脂)与PLGA(聚乳酸-羟基乙酸共聚物)两种材料结合,利用超声复乳法制备聚合物脂质纳米球,采用响应面法优化最佳制备工艺;以HSPC(氢化大豆卵磷脂)与PLGA(聚乳酸-羟基乙酸共聚物)的比例、PVA浓度、超声功率为条件优化制备参数,以粒径为响应值。结果:优化后的最佳工艺参数为:HSPC与PLGA的比例为1:10,PVA浓度为0.66%,超声功率为51.34%(205.36 W)。结论:按最优工艺制备出的聚合物脂质纳米粒的粒径为230 nm左右,多分散系数(PDI)值为0.057,与预测值偏差较小,且粒径分布均一,可作为蛋白及多肽类药物的递送载体。     

生物可降解嵌段共聚物在给药载体中的应用

生物可降解嵌段聚合物因具有双亲性 ,靶向药物到特定部位等优点大大推动了作为给药载体系统的发展。本文综述了生物可降解嵌段聚合物在表面修饰、水凝胶、胶束、生物大分子载体系统中的应用     

聚乙烯醇复合水凝胶外用膜剂的制备与性能*

摘要目的：考察PVA/ 葡聚糖/ 羧甲基纤维素钠复合水凝胶外用膜剂的制备方法,并与纯PVA 水凝胶贴膜进行对比,考察本膜 剂在物理性能和药物体系的体外释放行为上所具备的优越性。方法：利用冷冻-解冻物理交联方法制备水凝胶装载胰岛素模型药 物的外用膜剂,通过万能拉力机和差示扫描量热法考察膜剂的物理性能,利用高效液色谱法考察该膜剂的体外释放行为。结果： PVA复合水凝胶外用贴膜相较于纯PVA水凝胶贴膜的韧性减小、刚性增加,体外释放变好。结论：通过将具有材料友好性的PVA 和多糖葡聚糖、羧甲基纤维素钠合并使用制备胰岛素复合水凝胶贴膜,既能保证贴膜具有良好的物理性能,又具有较好地释放行 为,优于目前文献报道的纯PVA水凝胶贴膜性能,有望继续研究优化性能。     

超声靶向微泡破坏与载药/载基因纳米粒联合应用的生物物理学机制及应用研究进展

超声靶向微泡破坏(ultrasound-targeted microbubble destruction, UTMD)能够安全、高效、简便地递送药物与基因,是当前超声医学领域的研究热点,其机制主要涉及超声辐照微泡引起的空化效应及其二级效应、内吞作用与声辐射力。近年来,随着生物医学材料科学迅猛发展,纳米载药系统取材更加广泛,制备方法愈发精良,载药量日益提高。将纳米载药系统与UTMD进行联合,可以扬长避短,为肿瘤等多种疾病的治疗带来新的思路与希望。本文旨在对UTMD与载药/载基因纳米粒联合应用的生物物理学机制及应用研究进行综述并提出展望。     

载HCPT纳米粒的制备及其体外抗肿瘤活性研究

目的:制备载羟基喜树碱(HCPT)的PLGA-hyd-PEG-FA纳米粒(HCPT@PLGA-hyd-PEG-FA),并对其体外抗肿瘤活性进行研究。方法:采用乳化溶剂挥发法制备HCPT@PLGA-hyd-PEG-FA,通过单因素试验考察超声功率、聚合物浓度、PVA浓度、水相和油相体积比及投药量对纳米粒粒径的影响;采用zeta电位及激光粒度分析仪测定纳米粒的粒径及zeta电位,用透射电镜(TEM)观察其形态;采用透析法评价HCPT@PLGA-hyd-PEG-FA的体外释药特性;采用MTT法测定HCPT@PLGA-hyd-PEG-FA对HepG2细胞的细胞毒性。结果:HCPT@PLGA-hyd-PEG-FA平均粒径约为109±3 nm,zeta电位为-11.57 mV,载药量为5.6%,TEM显示其为球形;体外释药结果表明HCPT@PLGA-hyd-PEG-FA对HCPT的释放具有p H值依赖性;HCPT和HCPT@PLGA-hyd-PEG-FA的IC50值分别为474.6 ng/mL和286.0 ng/mL。结论:HCPT@PLGA-hyd-PEG-FA体外释药性能良好,HCPT@PLGA-hyd-PEG-FA的细胞毒性明显大于游离的HCPT,值得进一步研究。     

Difference in concentration dependence of relaxation critical exponent N for alginate solutions at sol-gel transition induced by calcium cations

The sol-gel transition in aqueous alginate solutions induced by chelation with calcium cations from in situ release has been investigated with viscoelastic methods. Two alginate samples having different molecular weights (MW) were used over the concentration C(Alg) of 2 approximately 6 wt % with different mole ratio f of Ca2+ to the alginate repeat unit. The gel point f(gel) and relaxation critical exponent n were determined according to Winter's criterion, the later agrees well with that obtained from the relaxation modulus. The results indicate that the power law is valid for the dynamic relaxation at the gel point and the critical gel possesses the self-similarity in structure. With increasing C(Alg), f(gel) for the alginate with lower MW decreases dramatically and n is almost constant of about 0.71. In contrast, f(gel) for the higher MW alginate with is almost a constant and n decreases from 0.72 then levels off at 0.37 with increasing C(Alg), indicating that the concentration dependence of n varies with MW of alginate in the starting solution. The fractal dimension d(f) estimated from n suggests a denser structure in the critical gel of higher MW alginate. Either n or d(f) has been found to follow one curve for the two samples if plotted against the number of cross-link junctions per polymer chain, which is proportional to the alginate MW.     

Rheological and structural properties of aqueous alginate during gelation via the Ugi multicomponent condensation reaction

Turbidity, structure, and rheological features during gelation via the Ugi multicomponent condensation reaction of semidilute solutions of alginate have been investigated at different polymer and cross-linker concentrations and reaction temperatures. The gelation time of the system decreased with increasing polymer and cross-linker concentrations, and a temperature rise resulted in a faster gelation. At the gel point, a power law frequency dependence of the dynamic storage modulus (G' proportional, variant omega(n)(')) and loss modulus (G' ' proportional, variant omega(n)(' ')) was observed for all gelling systems with n' = n' ' = n. By varying the cross-linker density at a fixed polymer concentration (2.2 wt %), the power law exponent is consistent with that predicted (0.7) from the percolation model. The value of n decreases with increasing polymer concentration, whereas higher temperatures give rise to higher values of n. The elastic properties of the gels continue to grow over a long time in the postgel region, and at later stages in the gelation process, a solidlike response is observed. The turbidity of the gelling system increases as the gel evolves, and this effect is more pronounced at higher cross-linker concentration. The small-angle neutron scattering results reveal large-scale inhomogeneities of the gels, and this effect is enhanced as the cross-linker density increases. The structural, turbidity, and rheological features were found to change over an extended time after the formation of the incipient gel. It was demonstrated that temperature, polymer, and cross-linker concentrations could be utilized to tune the physical properties of the Ugi gels such as structure, transparency, and viscoelasticity.     

Novel injectable pH and temperature sensitive block copolymer hydrogel

A novel pH and temperature sensitive block copolymer was prepared by adding pH sensitive moiety to temperature sensitive block copolymer. This block copolymer solution showed a reversible sol-gel transition by a small pH change in the range of pH 7.4-8.0 and also by the temperature change in the region of body temperature. The very precise molecular weight control of block copolymer and the prudential tuning of hydrophilic-hydrophobic balance were needed to control the phase diagram. This block copolymer solution forms a gel at 37 degrees C, pH 7.4 (human body). When the block copolymer solution is at room temperature and pH 8.0 as a sol state, both the temperature and pH change are needed for the gelation. This material can be employed as injectable carriers for hydrophobic drugs and proteins, etc. Gelation inside the needle can be prevented by an increase in the temperature during injection, because it does not change into the gel form with only increasing temperature. This material can be used for even a long guide catheter into the body. The block copolymer hydrogel which shows the sol-gel transition by the small pH change from pH 8.0 to pH 7.4 has merits in the delivery system for protein and cells which show cytotoxicity in acidic (below pH 6.5) or basic (above pH 8.5) conditions. This block copolymer system could be used as a template technology for injectable delivery systems.     

The effects of temperature on the cytochrome P-450 system of thermally acclimated bluegill

The effects of temperature acclimation at 10, 20 and 30 degrees C on the concentration and activity of the mixed function oxidase system in bluegill are as follows. Liver weight/body weight varied inversely with temperature. Significant (P less than 0.05) differences in concentration of cytochrome P-450 of hepatic microsomes were seen and varied inversely with temperature. Benzo(a)pyrene hydroxylase activity tested in vitro at incubation temperatures of 10, 20 and 30 degrees C showed significant differences in Km, but no differences in Vmax. SDS polyacrylamide gel electrophoresis revealed some quantitative differences in cytochrome P-450 isozymes between groups.     

In vitro and in vivo release of albumin using a biodegradable MPEG-PCL diblock copolymer as an in situ gel-forming carrier

An MPEG-PCL diblock copolymer was synthesized as an in situ gel carrier, and its phase transition behavior in aqueous solutions was examined. For comparison, aqueous solutions of Pluronic F-127, a widely used injectable gel-forming solution, were also studied. Both MPEG-PCL copolymer and Pluronic aqueous solutions were sols at room temperature. As the temperature was increased above room temperature, the diblock copolymer and Pluronic solutions underwent a sol-to-gel phase transition, which manifested as an increase in viscosity indicative of the formation of a gel. All of the copolymer solutions became gels at body temperature, although the gel viscosity increased with the increasing concentration of the MPEG-PCL diblock copolymer in the solution. In in vitro experiments, in which the gels were exposed to PBS, the MPEG-PCL gels maintained their structural integrity for more than 28 days, whereas the Pluronic gel disappeared within 2 days. The same results were observed when the polymer solutions were subcutaneously injected into rats. The MPEG-PCL gels maintained their structural integrity longer than 30 days, while the Pluronic gel could not be observed after 2 days. The ability of the gels as drug carriers was studied by measuring the release of fluorescein isothiocyanate-labeled bovine serum albumin (BSA-FITC) from MPEG-PCL diblock copolymer gels in vitro as well as in vivo. In vitro, BSA release was sustained above 20 days, with a greater release at lower diblock copolymer concentration; by contrast, Pluronic gels exhibited almost complete release of BSA-FITC within 1 day. When the BSA-FITC-loaded diblock copolymer and Pluronic solutions were subcutaneously injected into rats, they immediately transformed into a gel. In vivo, sustained release of BSA-FITC over 30 days was observed from the MPEG-PCL gel, whereas BSA-FITC release from the Pluronic gel ceased within 3 days. Collectively, the present findings show that MPEG-PCL diblock copolymer solutions are thermo-responsive and maintain their structural integrity under physiological conditions, indicating that they are suitable for use as injectable drug carriers.     

Rheological and calorimetric study of the sol–gel transition of κ-carrageenan

Rheological and DSC techniques were used to study the effect of κ-carrageenan and KCl concentrations, 0–300 mM, on the sol–gel transition as well as on the linear viscoelasticity, at 25 °C, of the resulting gels. In heating and cooling DSC tests, the peak temperature was taken as the sol–gel transition point. In rheological tests, sol–gel transitions were determined from the variation of dynamic moduli with frequency and temperature, the independence of the phase angle on frequency and the evolution with temperature of dynamic moduli on cooling and heating at constant frequency and strain. Transition temperatures from DSC and rheology were in good agreement among them and with those previously reported. The three procedures yielded similar results, but the transition temperatures were more easily determined through the independence of the phase angle on frequency. Frequency sweeps showed gel behavior with stiffness increasing with polysaccharide and salt concentration. Below 100 mM KCl, G′ increased notably, whereas higher concentrations produced only marginal increases.     

Viscoelastic properties of human tracheobronchial mucin in aqueous solution

Human tracheobronchial mucin isolated from cystic fibrosis patients (CF HTBM) was purified using a combination of gel filtration and density gradient centrifugation. The resulting mucin was fractionated to reduce polydispersity and to facilitate studies of the molecular weight dependence of mucin viscoelasticity in concentrated solution. The viscoelastic properties of CF HTBM were examined in distilled water, 0.1M salt solutions and chaotropic solvents. In controlled strain experiments (strain ≥ 5%) with increasing mucin concentration, a crossover from sol to gel behavior is observed. The gel strength, as measured by the magnitude of the storage modulus at comparable mucin concentrations, is greatest for distilled water, intermediate for 0.1M NaCl, and lowest far 6M GdnHCl. In distilled water, high molecular weight mucin undergoes a sol-gel transition at ～ 12 mg/mL, and shows evidence of a plateau modulus at higher concentrations. The storage and loss moduli of concentrated high molecular weight fractions in 6M GdnHCl exhibit a power law dependence on frequency typical of weak gels near the sol–gel transition at 20 mg/mL. Similar rheology is observed in 0.1M NaCl and 0.091M NaCl/3 mM CaCl₂, but with evidence for additional weak associations at low frequency. The power law exponent in these systems is 0.70 ± 0.02, in good agreement with prediction for networks formed by a percolation mechanism. Low molecular weight fractions in these solvents exhibit a fluid-like viscoelastic response. However, low molecular weight mucin in distilled water shows a strain-dependent increase in elasticity at low frequency indicative of weak intermolecular associations. Comparison of the rheological behavior of CF HTBM with our earlier studies of ovine submaxillary mucin lends support to the idea that carbohydrate side-chain interactions are important in the gelation mechanism of mucins. © 1995 John Wiley & Sons, Inc.     

A Rapidly Labeled RNA Component Isolated from Posterior Silkgland of Silkworm

The effects of NaCl and heating temperature on the gel-forming ability of legumin were studied. The addition of NaCl progressively increased the denaturation temperature of legumin. Heating to around the denaturation point, i.e., below the onset temperature (zone 1), between the onset and maximal temperatures (zone 2), between the maximal and final temperatures (zone 3), and above the final temperature (zone 4), affected both the gel-forming ability and gel properties. No gel was formed in zone 1, while the gel was harder in zone 3 than in zones 2 and 4. The gel hardness gradually decreased with increasing temperature in zone 4. Differences in the viscoelastic and microstructural properties between gels heated at various temperatures around the denaturation point were observed.     

Relationship between state of aggregation and catalytic activity for cytochrome P-450LM2 and NADPH-cytochrome P-450 reductase

The detergent 1-O-n-octyl-beta-D-glucopyranoside (octylglucoside) was found to replace the phospholipid requirement in the demethylation of benzphetamine by cytochrome P-450LM2 and NADPH-cytochrome P-450 reductase purified from phenobarbital-treated rabbit liver. At low enzyme concentration (0.1 microM) in the absence of glycerol and phosphate, the maximum rate of benzphetamine-specific NADPH oxidation was approximately 35% of that observed in the presence of dilauroylglyceryl-3-phosphoryl choline. At higher enzyme concentration (2.5 microM) and in the presence of 0.15 M phosphate, 20% glycerol, octylglucoside was as effective as phospholipid in stimulating the production of formaldehyde from benzphetamine. The detergent concentration required for maximal enzymatic activity was 2.5-4.0 g/liter, depending on the cytochrome preparation used. At higher octylglucoside concentrations (5-7 g/liter), activity decreased to zero, although neither enzyme appeared to be irreversibly denatured at these detergent concentrations. Sedimentation equilibrium experiments with P-450LM2 alone or in the presence of equimolar reductase showed that increasing octylglucoside levels promoted disaggregation of the cytochrome. Pentamers and hexamers predominated at detergent concentrations where maximal activity was observed, while higher levels of detergent where activity was absent produced cytochrome dimers and, ultimately, monomers. The reductase was monomeric at detergent levels between at least 3 and 7 g/liter. Moreover, both gel filtration and sedimentation equilibrium experiments demonstrated that a stable complex between P-450LM2 and its reductase was not formed at octylglucoside concentrations where high activity was evident. These results are consistent with a model of P-450/reductase interaction in which functional aggregates of three to six cytochrome polypeptides move laterally in the microsomal membrane and interact with the reductase by random collision.